The effect of positive end expiratory pressure on lung mechanics and arterial oxygenation after open heart surgery in young children.

The effect of positive end expiratory pressure (PEEP) during mechanical ventilation of the lungs was measured in 10 young children, aged 3 weeks to 30 months, who were being ventilated artificially after cardiopulmonary bypass surgery. Changes in the end-tidal lung volume were measured directly using a jacket plethysmograph, and were assumed to indicate change in functional residual capacity (FRC). Simultaneous changes in compliance and blood-gases were measured also. FRC was increased in all subjects, and in most this increase was accompanied by an increase in arterial oxygenation. There was no significant alteration in the mean values of dynamic or static compliance in the group, although dynamic compliance increased during PEEP in six patients. PEEP may be of value after cardiopulmonary bypass in young children when oxygenation is poor despite high inspired oxygen fractions. The possible mechanisms by which it increases PaO2 are discussed.